The present invention relates to a stacking device for a prefolded endless paper-web in a paper stacker, in which the paper-web is atacked on a paper support which is adapted to move downwardly in accordance with the stack height, and which is provided with a compensating element adapted to elevate central portion of the paper stack with respect to the folded edges thereof.
In printer devices employing folded endless paper webs which are to be processed, following the particular processings, the paper web must again be laid down or stacked in folded relation. Units of this type include, for example, mechanical and non-mechanical high-speed printers, in which such units are followed by paper stackers into which the printed paper web is deposited. In this operation the prefolded paper web is laid down in zig-zag layers one above the other in the paper stacker.
In a non-mechanical printer, the standard endless paper, upon passage through the machine, becomes highly heated in the fixing station of the printer, as a result of which the paper acts as if it were in effect being "ironed out". Thus, it stretches and the previously formed folds lose their definition. Even though the paper is laid down with the folds in the correct relative positions, and irrespective of the application of corresponding pressure applied by known type of paddle spindles which are normally provided, it is difficult to reform the stack with its original height and shape. This becomes particularly difficult when relatively light papers are being processed. With increasing stack height, the stack build-up at the edges in the vicinity of the transverse folds, becomes substantially higher than at the central portion of the stack, forming a depression thereat which makes it impossible to achieve proper deposition of the paper, sheet by sheet.
A stacking device is known from U.S. Pat. No. 3,640,521, in which, in a high-speed printer, prefolded endless paper-web is stacked on a paper support, which support is lowered as the height of the paper stack increases. In an effort to avoid the formation of a depression due to the increased height of the transverse fold, an elevated lift member is provided on the paper support, and in addition the paper stack is guided at the front and rear by suitable guide bars.
However, the attachment of a fixed compensating element to the paper support has the disadvantage that it enables only a medium-sized folded paper stack to be suitably compensated. Thus, a paper stack of relatively low height will receive too much upward deflection and a paper stack of relatively greater height will receive too little.